1. Field of the Invention
In very many applications it is required to employ pulleys in order to transmit a rotating movement, raise loads, vary the direction of a cable, etc.
2. Description of the Related Art
Normally the pulleys (or generally a rotating wheel) are fixed to the pin on which they rotate either permanently or otherwise via fixing means which range from split pins to bolt-type fastening systems. Not infrequently the pulley must be removed from the pin by means of a very quick and simple operation, for example so as to replace it with a different pulley.
An example of this arises in the sector of tubular gearmotors to which reference will now be made by way of example.
Tubular gearmotors for moving and/or automating roller blinds, such as shutters, blinds and curtains, at present are designed in such a way that they may be inserted inside a winding drum on which the said shutter is wound (and unwound). They comprise principally an electric motor, a speed reducer and a capacitor, which are housed inside a tubular body. Two pulleys for transmission of the rotating movement from the gearmotor to the winding drum are provided at the ends of the metallic tubular body.
The transmission pulleys have a grooved external profile which matches the internal form of the winding drum. The first pulley is mounted on an output pin of the gearmotor, while the second pulley is mounted on the end-of-travel mechanism. The invention relates to the first pulley.
Usually this pulley is fixed to the rotating pin either with permanent fixing means (screws, washers, etc.) or by means of a tongue arranged on the rotating pin. The tongue engages inside a corresponding seat of the pulley once the latter has been inserted on the pinion. The pulley also has, formed in it, a groove inside which a screwdriver can be inserted in order to lower the tongue and extract the pulley from the pinion.
This solution has the disadvantage that the pulley replacement operation requires precisely the insertion of a screwdriver, for which the installation operator must use one hand, while with the other hand the pulley must be removed.
If one considers that very often replacement is performed once the gearmotor has been installed and therefore in a position which is not easily accessible (for example inside the recess of a wall reached by means of a ladder), it is easy to appreciate the awkward nature of this operation and the danger of not being able to hold on with at least one hand.